I think its a deformaty braught on during the manufacturing process where the paper which ensures the cigarette burns evenly is dis proportioned, I think it has less or more of the chemichals and thus burns at a different rate.

a.there are on occasion small insects which feed and live among tobaccoo. these are occasional compacted and pressed into cigs.

b.they did not refine tobacco in yer cig and crackle is akin to a seed popping.

or you where given the packet and it was one of those date rape smokes. which do exist. was rather popular in edinburgh not to long ago. met a girl who was nearly rapped because of it, it was even on news at time.